The typical time pressures encountered by a traveler meeting airplane or train schedules are often complicated by large, cumbersome and/or heavy suitcases or articles of luggage. In order to avoid the direct carrying of such luggage, individual articles of luggage are characteristically rendered movable along an underlying ground surface by the provision of a number of wheel or castors attached to the bottom surface of the luggage such that the wheels may freely spin in a direction of travel and, in some cases, pivot about an axis defined substantially perpendicular to the bottom surface. Each piece of movable luggage also classically possesses a strap or other handle positioned on the top surface or along a side or front face thereof for pulling the luggage along the ground surface and for carrying the luggage from place to place.
The pulling forces for causing such wheeled luggage to move from a resting position to a moving state along the ground surface, or for changing the direction of motion while the luggage is in the moving state, are generally directed to a point located at or above, and most typically substantially higher than, the center of gravity of the luggage. As a consequence, the pulling forces required to move such luggage can easily result in tipping or misdirection along the ground surface. Turning or redirecting of the luggage from a stopped position or while it is in motion requires overcoming the then-current inertial forces by pulling, pushing or twisting the handle or strap in order to translate and distribute turning forces through the luggage to the pivotal axes of the wheels or castors. In this manner, the wheels are turned via such translated forces to change the direction of travel. It can therefore be appreciated that greater force is required to turn such an article of wheeled luggage than to move the article in a straight direction, since a component of the forces exerted must first turn the entire mass of the article to turn the wheels attached thereto, leaving the remaining component for moving the article in its new direction. Moreover, the handle or strap attached to the luggage, through which these forces are applied and distributed, is stressed, and a potential point of failure is established at the point of attachment of the handle. Additionally, changing the direction of motion of the luggage is frequently rendered slow, difficult and imprecise as a consequence of the need to pull, push or twist the handle in order to translate these forces from a twisting action of the mass or weight of the luggage to a pivoting action of the wheels or castors about their pivotal axes. As a consequence, such devices are intrinsically restricted in their freedom of motion as a result of their design and are substantially ineffective and inefficient in their energy-input requirements and in their capacity to suitably distribute the forces for motion.
Castors for container supports, in contrast to those provided for moving luggage along a flat surface, have been known in the art. For example, in U.S. Pat. No. 1,975,291 to Ritter, Jr., a series of castors provide for rotary support of a trunk having opposingly disposed luggage compartments to enable manipulation of the closure of the trunk without requiring a shift or change in position by the operator. However, Ritter, Jr.'s castors are not utilized for moving the luggage along a flat surface.
As shown in U.S. Pat. No. 2,605,989 to Luft, roller assemblies have been used as a turntable base for moving luggage along a flat surface or floor and for providing pivoting of the piece of luggage upon the assembly to which it is attached. However, for the same reasons set forth above, Luft's rolling assemblies are restricted in their freedom of motion and are inadequate in their distribution of the forces required for moving the luggage and changing its direction of motion.
The use of castor mountings for luggage is also known in the art. For example, in U.S. Pat. No. 3,526,921 to Aupke, castors are provided along a bottom face of a suitcase and are removably mounted through socket apertures drilled or punched in the bottom face. Aupke's castors possess the drawbacks described above, i.e., pivoting is imprecise and difficult, and the forces for moving the suitcase are presented at a location that lies a substantial distance above the center of gravity, rather than directly to a pivoting point. Consequently, freedom of motion of Aupke's luggage is restricted, and the forces must be distributed through the handle which, in Aupke's device, is the same handle used for carrying the luggage.
A luggage handle doubling for both carrying and moving a piece of wheeled luggage is also disclosed in U.S. Pat. No. 4,838,396 to Krenzel. Krenzel's luggage handle enables the user to maintain a relatively upright position while dragging the case along a ground surface. The rear face of the luggage equipped in accordance with Krenzel's device possesses a single front castor wheel and non-pivoting rear wheels, i.e., wheels which do not pivot about an axis substantially perpendicular to the rear face of the luggage. Such wheeled luggage possesses the same drawbacks described above and, in addition, the single front wheel provides seriously diminished stability in maintaining the luggage in an upright condition as it is moved along an underlying support surface.
A removable luggage carrier is also described in U.S. Pat. No. 3,861,703 to Gould in which each of four separate castor wheels is mounted on a plate that is attached by Velcro fasteners to a side or rear face of and proximate a respective corner of an article of luggage. The luggage handle normally used for carrying the article equipped with the Gould device is also employed for moving the luggage along a flat surface upon the detachable castor assemblies. Thus, Gould neither addresses nor overcomes the problems discussed above.